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    <title>SNAP Data Processors - ARC Algorithm Specification </title>
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        <td class="header">&nbsp;
            ARC - Algorithm Specification</td>
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<p>Algorithm Specification of the science processors of the SNAP Toolbox</p>

<h3>Saharan Dust Detection</h3>

<p>
    Dust aerosol can be a problem for some satellite SST products as infrared SST
    retrievals are biased cold in the presence of dust. While very high dust loadings
    are often (incorrectly) flagged as "cloud", more moderate amounts are passed as
    "clear" and impact the resulting SST fields. This is a particular problem over the
    Atlantic in the summer months when desert dust is lifted from the Saharan desert and
    transported west over the ocean.
</p>

<p>
    Desert dust is detected using the ATSR Saharan Dust Index (ASDI) method described in
    <object classid="java:org.netbeans.modules.javahelp.BrowserDisplayer">
        <param name="content" value="http://dx.doi.org/10.1016/j.rse.2010.06.016">
        <param name="text" value="<html>Good et al. (2011)</html>">
    </object>.
    This functions as a dual-view retrieval of dust index using the 11 and 12 micron channels
    which can therefore be used both day and night.
</p>

<h3>SST Retrieval</h3>

<p>
    ARC SSTs are estimated using a coefficient-based retrieval scheme (
    <object classid="java:org.netbeans.modules.javahelp.BrowserDisplayer">
        <param name="content" value="http://dx.doi.org/10.1016/j.rse.2010.11.020">
        <param name="text" value="<html>Embury and Merchant 2011</html>">
    </object>) which is robust to the presence of stratospheric aerosol from the Mount Pinatubo
    eruption in 1991. The coefficients are banded by: total column water vapour (TCWV)
    to reduce the effects of atmospheric variability on the nadir and day-time
    retrievals; satellite zenith angle to reduce viewing angle dependent biases from the
    dual-view geometry.
</p>

<h3>SNAP implementation</h3>

<p>
    TCWV data is provided in SLSTR inputs; however, it is not included with ATSR L1b files.
    As a result the user must supply the TCWV data when processing ATSR scenes.
</p>

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